In 2002, Ellen Klages was not an aspiring novelist; she had never written a novel. Her metier was science fiction short stories—for grown-ups, not kids. So when Viking editor Sharyn November, who had read some of her published work, approached her at an SF convention and said, "You are a children's writer. You need to write me a children's book," Klages was, understandably, taken aback. "I found myself thinking, 'An editor at Viking wants me to write a book for her? What part of that should I ignore?'

So Klages went home, cast aside doubt, and did as she was told. The result, The Green Glass Sea, was published by Viking.

Klages, 52, wasn't a total stranger to writing for children; she had co-authored a number of books for San Francisco's Exploratorium, a children's science museum. But what attracted November's attention was the way she characterized kids in her writing for adults. "The children in her stories are absolutely true," she says. "It's rare you see an author capture that with such a degree of accuracy."

The novel Klages wound up writing arose from background reading about the Manhattan Project's atomic bomb testing in New Mexico. She came across a fact about the detonation that startled her: the 100-million-degree heat had fused 75 acres of desert sand into jade-green glass. "Then I read that some of the scientists took their families to the site for a picnic and I thought, 'Oh, what a tremendously bad idea.' "

But a great backdrop for a short story; Klages wrote a 4,000-word piece and remembers there was stunned silence after she read it in public the first time. "I thought, 'Either this really didn't work or it really did.' "

She hadn't placed the story when November asked her to write a children's book. Now she had a good excuse to return to her radiation-laced picnic site, where she felt she had plenty to more to write about the two girls she had created: unlikely friends who meet and bond while their scientist parents are working with the Robert Oppenheimer team to develop the bomb. She worked backwards from the short story, which became the last chapter of her first book.

November's hunch about Klages paid off. Penguin's sales reps picked The Green Glass Sea as their favorite title of the fall list, Book Sense made it a No. 1 pick and PW called it "an impressive debut" that "brings to life the tensions of war experienced by adults and children alike."

Klages no longer needs to be persuaded to write for children. She is already at work on a sequel—"I'm surrounded by the entire run of Popular Mechanicsfrom 1946 and 1947"—while awaiting the spring publication of her first story collection, Portable Childhoods (Tachyon).

"When I won the Nebula Award last year, I thought that was the best day of my life," she says. "But so many good things keep happening, I've had to rethink that."